When Evelyn is talking to Jake on the couch, his knees are at first bent backwards, indicating he is sitting on his feet. Once the camera angle switches, however, Jake is sitting cross-legged and his feet are visible. Jake is never shown shifting his position during the conversation.
Since Charlie had just put his sleepwalking brother back to bed and he was outside his brother's room (which is just down the hall from Jake's) with Rose, how did Jake get behind the refrigerator door without Charlie seeing him? The camera angle showed the area behind the refrigerator door as Charlie opened it and Jake is not seen walking up behind the open door while Charlie is getting his drink. Apparently, the way the scene was laid out, there wasn't time to show Jake actually walk into the scene. EDIT: There is nothing that definitively indicates that Jake was in his room when Charlie put Alan back in his (Alan's) room. For whatever reason, Jake could have been in the laundry room or another part of the house entirely.
When Rose startles Charlie, who has just put the sleepwalking Alan back to bed, he stumbles against a prop wall, rocking it noticeably.